Valve system

ABSTRACT

An air diverter valve for selectively diverting the output of an air pump in a vehicular emission control system from a combustion system to a diversion system, in response to each or all of a variety of system conditions including abrupt rise in intake manifold vacuum, continuing low intake manifold vacuum, continuing high intake manifold vacuum, or overtemperature conditions, and for controlling the duration of the diversion.

mted States Patent 1 1 1 1 3,805,522 Sheppard Apr. 23, 1974 [54] VALVESYSTEM 3,059,419 /1962 Schnabel 60/290 3,433,242 3 1969 V 0 290 [75]Inventor: William L. Sheppard, Romulus, 3,523,418 8x970 2252: 2 Mlch-3,591,961 7/1971 Woodward 60/290 [73] Assignee: AVM Corporation,Jamestown,

NY Primary Examiner-Douglas Hart Filedl 1971 Attorney, Agent, orFirm-Harness, Dickey & Pierce 21 Appl. No.: 195,631

Related [1.8. Application Data [63] Continuation-impart of Ser. No.126,182, March 19, [57] ABSTRACT 1971, abandoned. .1

An air diverter valve for selectively diverting the out- [52] US.Cl..... 60/290, 60/291, 137/1 19, put of an air pump in a vehicularemission control sysl37/489.5, 251/45, 417/282, 417/307 tern from acombustion system to a diversion system, [51] Int. Cl. F0ln 3/00 inresponse to each or all of a variety of system condi- Field of Searchtions including abrupt'rise in intake manifold vacuum, 60/292; 417/307,282, 290; 137/ll9, 489.5, continuing low intake manifold vacuum,continuing 495; l/ high intake manifold vacuum, or overtemperatureconditions, and for controlling the duration of the di- [56] ReferencesCited version.

- UNITED STATES PATENTS 2,851,852 9/1958 Cornelius 60/290 20 Claims, 12Drawing Figures /4 r 7' my! 14 I 4 2 /4 )7 b: g [var/a7 w M l W l f7 v7/ l 710%; N 70 vii/1:412)

PATENTEDAPR 2 3 I974 sum 1 UF 4 VALVE SYSTEM CROSS REFERENCE TO RELATEDAPPLICATION The present application is a continuation-in-part ofapplicants earlier filed application Ser. No. 126,182, filed Mar. 19,1971, entitled Valve System, now abandoned.

SUMMARY OF THE INVENTION In order to reduce undesirable vehicularexhaust emissions, and particularly the emission of unburnedhydrocarbons, automobile manufacturers have utilized systems forinjecting fresh air into the exhaust systems of internal combustionengines to produce additional combustion of the unburned hydrocarbonsemitted through the exhaust valves of the engine. In one such system,for example, (the so-called injector reactor system used by GeneralMotors Corporation), an air pump drives fresh air, under pressure,through air manifolds, hoses and injection tubes into the exhaust systemof the internal combustion engine in the area of the exhaust valves. Adiverter valve, sensing and operated by the intake manifold vacuum ofthe engine, responds to a sharp increase in manifold vacuum diverts thepumps output air flow from the utilization system (here, the exhaustsystem) to atmosphere (through a muffler) to prevent backfiring duringthis period of richer mixture.

The present valve is designed to better perform that function, as wellas other functions.

In addition, similar air pumping systems will likely be used inconjunction with so-called catalytic converters or other supplementarycombustion systems used in lieu of or supplemental to the vehiclesmuffler to provide the fresh air necessaryfor the additional combustionof output exhaust products from the engine, and those systems willlikely also utilize a diverter valve to selectively divert the pump airfrom the utilization system (here, the combustion device. such as thecatalytic converter or other system) to a diversion system, which maybe, for example, exhaust to atmosphere, mm the inflow port of the pumpitself. Again, the present valve is designed to perform that functionunder each or all of a variety of system conditions.

THE DRAWINGS FIG. 1 is a cross-sectional view, partially fragmentary, ofa diverter valve system embodying the principles of the presentinvention;

FIG. 1A is a fragmentary cross-sectional view of an auxiliary valveelement which may be substituted for or used additionally to a portionof the system of FIG. 1;

FIG. 2 is a series of curves reflecting the operation of the device ofFIG. 1 under certain operating conditions;

FIG. 7 is a view illustrating a method of assembling a portion of thevalve of FIG. 1 to achieve uniformity of product;

FIG. 8 is a cross-sectional view, partially fragmentary, of a modifieddiverter valve system including an overtemperature sensing capability;

FIG. 9 is a fragmentary view of an alternative overtemperature sensingarrangement for association with the modified diverter valve of FIG. 8;

FIG. 10 is a schematic representation of a modification of the system ofFIG. 9;

FIG. 11 is a schematic representation of a further modification of thesystem of FIG. 9; and

FIG. 12 is a cross-sectional view, partially fragmentary, of a modifieddiverter valve.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION The valvesystem of FIG. 1 is illustrated in association with, and includes,elements of a positive air pressure generating system, such as a pump,having an outflow port 10 defined by housing elements 12, 14, 16 and 18,all of which are normally integral and may be elements of the pumphousing itself or elements of a conduit .from the pump. Air from port 10normally flows through port 20 to the utilization device or system, suchas the exhaust system of the vehicle, or the catalytic converter 22. Adiversion port 24 (illustrated to be formed in the housing elements 14and 18) may extend to atmosphere or back to the input or suction port ofthe pump. Diversion port 24 is illustrated to have a conical valve seat26 at its entrance which is illustrated to be engaged by a valve 30mounted on a valve stem 32. When valve 30 is closed, as illustrated, thepump air flow is through outlet 20 to the utilization device. When valve30 is opened (moved to the left in the view of FIG. 1) the major airflow from the pump is diverted through port 24 since the impedance toair flow through that port is small relative to the impedance to airflow through port 20 and through the utilization device, particularly ifport 24 is connected to the input of the pump. Accordingly, it is notessential that movement of the valve stem 32 also move another valveinto sealing engagement with output port 20, although such can be doneif desired.

When valve stem 32 moves to the right to bring valve 30 into sealingengagement with seat 26, problems of sealing and problems of alignmentbetween the longitudinal axis of movement of stem 32 and the centralaxis of valve seat 26 can occur with an economically priced system.Accordingly two things are done. First, the sealing surface 34 of valve30 is desirably a spherical surface (formed on a radius) to provide linesealing contact with the conical seat 26. Secondly, valve 30 is mountedon stem 32 in a manner to permit valve 30 to adjust itself radially(relative to the longitudinal axis of stem 32) to self-center andself-seat in conical valve seat 26 even though the aforesaid alignmentdoes not exist in the particular valve at that particular time. To thatend, stem 32 is provided with a reduced-diameter of necked-down portion36 near its end, defining a shoulder 38. Annular valve 30, which issupported on portion 36, is provided with a central, circular, aperture40 which accepts the reduced-diameter portion 36 of stem 32. To theright of valve 30, stem 32 is further necked-down to accept a retainingring 42 which retains valve 30 on stem 32. To permit radial adjustmentof valve 30 relative to the longitudinal axis of movement of stem 32,the aperture 40 in valve 30 is made larger than the reduced-diameterportion 36 of stem 32, although aperture 40 is sufficiently smaller thanthe diameter of stem 32 to the left of the valve so as to provide asealing engagement between the valve and the stem at the shoulder 38 atall radial positions of valve 30 and during the times in which valve 30is in abutment with valve seat 26. It is presently contemplated thatvalve 30 be made of nylon plastic and valve seat 26 and stem 32 bemetallic. in one design of the system, as some numerical examples, valve30 was 0.78 inches in outer diameter, the engaging surface 34 was formedon a 1 inch spherical diameter, aperture 40 had a diameter of 0.36inches, stem 32, in the region to the left of valve 30, had a diameterof 0.625 inches, and portion 36 of stem 32 had a diameter of 0.313inches.

The valve assembly of FIG. 1 includes a diaphragm or piston or movablewall portion 44 the central portion of which is clamped between a stopwasher 46 and a cup washer 48, that assembly being locked to thelefthand end of valve stem 32.

The outer periphery of diaphragm 44 is clamped between a body member 50(which may be plastic or die cast) and a cover stamping 52 which servesthe several additional functions of providing a means for mounting thevalve in place, of providing an area against which washer 46 may stop,of guiding stem 32 in its movement, and of defining, in conjunction withdiaphragm 44, a chamber 54 to the right of diaphragm 44. Body member 50includes a central recess which forms, with diaphragm 44, a chamber 56to the left of that diaphragm, body 50 being notched at 58 to insurethat cup-shaped washer 48 does not preclude the free flow of air in thechamber. Washer 48, in moving within chamber 52, also serves to guidethe movement of stem 32 and further helps to position and guide a spring60 which is mounted within the chamber 56 and operates in compressionbetween body 50 and washer 48, tending to move the central portion ofdiaphragm 44 and stem 32 toward the right to the illustrated position.

The positive pressure from the pump appearing at port is communicatedinto chamber 54 through a passageway 62 which is sufficiently large topermit the free flow of air into and from chamber 54 as the pressure inport 10 changes. The pressure in port 10 is further communicated tochamber 56 through a passageway 64 in stem 32, through taperedpassageway 66, and through orifice 68. Accordingly, under normal,relatively steady conditions, the pump pressure as it appears in port 10is established both in chamber 54 and in chamber 56. When valve 30 is inengagement with seat 26, its right hand face is subjected to thepressure in port 24 (which will normally be either atmospheric or belowatmospheric pressure). The left hand face of valve 30 is subjected tothe pressure in port 10 which is normally above atmospheric value. Thepressure in chamber 54, while operating on washer 46 and diaphragm 44,is not effective on that area thereof represented by the cross-sectionalarea of valve stem 32, whereas the pressure in chamber 56 actsessentially effectively upon the entire area of the left side ofdiaphragm 44, including washer 48. Those pressure differentials, coupledwith the force exerted by spring 60, (which is quite small) serve tohold valve 30 closed under the normal static conditions, as isillustrated in FIG. 1 of the drawings.

As will be seen, means are provided for abruptly reducing the pressurein chamber 56 in response to one type of signal condition in the systemwith which the apparatus is associated. When this occurs, a pressuredifferential appears across diaphragm 44 which produces leftwardmovement of valve stem 32 against the bias of spring 60 to disengagevalve 30 from valve seat 26, so as to divert the air through port 24. Inthat mode of operation, it is desired to restore valve 30 to its closedposition after a selected time. This is accomplished by metering airfrom port 10 into chamber 56 through orifice 68. The effective impedanceto air flow of orifice 68 controls the time required for reseating ofvalve 30 to occur. Tolerance variations can produce significantdifferences in the restoration rate from one valve to another in massproduced units. To achieve the desired consistency among those units,orifice 68 is calibrated on a per-valve basis by forming it (in thepreferred arrangement) in a plug 70 of deformable material andselectively deforming that material to effectively control the size oforifice 68. Thus, in the illustrated arrangement, plug 70 is made of amaterial which is more malleable or deformable than the material ofwhich stem 32 is made. As an example, plug 70 may be constructed ofso-called S grade aluminum which is a soft grade of aluminum. Stem 32may be formed of significantly harder aluminum, such as the gradedesignated T-3" or T-4." Desirably both the plug and the stem are of thesame type of material (e.g., aluminum) to match temperature coefficientsof expansion within adequate limits.

In the illustrated unit (FIGS. 1 and 6), the exterior of the centralportion of the plug 70 is a cylindrical surface (in the generic sense),representatively constructed by forming that central portion as acircular cylindrical surface, and then forming a cylindrical notch 68therein. As an example, in one design, the circular cylinder wasnominally 0.129 inches in diameter and the notch was formed as a portionof a circle having a 0.032 radius penetrating the surface of thecircular cylinder nominally 0.007 inches.

Plug 70 is inserted in tapered cavity 66 in stem 32. ln one design,cavity 66 is formed by drilling and then by reaming with a number 2/0taper pin reamer, reaming to a nominal 0.131 maximum diameter at theentrance 72 to the tapered chamber 66. The leading end of the plug 70 isdesirably chamfered to assist in centering the plug upon insertion inthe tapered cavity, and that chamfering is achieved by forming theleading end as a frusto-conical surface. In practice, both ends aredesirably made the same to facilitate assembly.

Referring to FIG. 7, plug 70 is desirably inserted in the cavity 66after washers 46 and 48 and diaphragm 44 have been assembled to stem 32but before the rest of the valve has been assembled. A drive pin, punch,or drift 74 is provided with a seat or cavity in its leading end whichis desirably conical or frustoconical and complementary to the shape ofthe trailing end of the plug 70. Drift 74 should be smaller in diameterthan the plug 70 so as to avoid any risk of deforming the metal adjacentorifice 68 (as by forming a burr), and the use of the conical end onplug 70 together with the conical cup in drift 74 providesself-centering to insure that drift 74 does not engage plug 70 in theregion of the slot 68. In one design, drift or punch 74 was selected tohave a diameter of 0.090 inches. Drift 74 is slidably sealed in achamber 75 which is also provided with an aperture 76. A seal 77,adjacent aperture 76, can be pressed into air sealing engagement withthe left hand end of stem 32. A source of positive air pressure 78 isconnected to chamber 75 through an orifice 79. A pressure gauge 80measures the pressure in chamber 75.

The plug 70 is first positioned at the entrance of the tapered cavity66. The unit including chamber 75 is then placed into sealing engagementwith stem 32, as noted. Punch or drift 74 is then pressed or tapped toforce plug 70 into cavity 66. The air from source 78 flows throughorifice 79 and through orifice 68, in se ries, to atmosphere. Hence, thereading of gauge 80 reflects the effective size of orifice 68. Thatgauge can be calibrated by using a standard valve to which productionvalves must conform. The operator continues to press or tap punch ordrift 74 to progressively force plug 70 further and furtherinto cavity66. During that driving motion, plug 70 is compressed and deformed, soas to effectively flow metal into the slot 68, reducing the effectivecross-sectional area thereof. Driving is discontinued when the gaugereading attains the preselected value. i

It is contemplated that other arrangements may be employed to producerelative distortion of the two metallic elements (with or without apermanent set) to achieve a functional determination of the correctorifice size to produce consistency ofperformance of the mass producedvalves. Obviously, the two parts need not be aluminum, and, as anotherexample, they could well be both manufactured of steel. The two partsshould have similar temperature coefficients of expansion. The necessityof progressive deformation of one or both of the parts dictates that atleast one must not be too hard or too rigid to accommodate thatdeformation. For example, it is contemplated that the tubular stem 32 bemanufactured with a substantially thinner wall than that illustrated,that is,'with the thickness between the wall of cavity 66 and theexterior of stem 32 much reduced from that illustrated, with the plug 70being provided with a flat instead of a groove and being driven withinthe cavity 66 in a manner to physically progressively distort the tube(with or without a permanent set) to-effectively reduce the gap betweenthe plug and the stem 32 with progressive insertion. Similarly, it iscontemplated that the tube be of a softer material than the plug so thatwhen the plug (grooved or with a flat) is progressively inserted, themetal of the tube will cold flow to progressively reduce the size of thecavity between the plug and the tube. Other variations will be apparentto those skilled in the art.

Referring again to FIG. 1, the generally cup-shaped body 50, which maybe, for example, plastic or a die casting, has, in addition to theperipheral lip against which diaphragm 44 is clamped, a central plateportion 81 including a central projection 82 having an air passageway 84extending longitudinally therethrough. The right-hand end of projection82 constitutes a valve surface 86 cooperating with a valve seat 88formed at the entrance to cavity 66 in valve stem 32. At the other endof passageway 84, a central valve seat 90 is formed in plate portion 81to cooperate with a valve 92. A further valve seat 94, which is annular,is formed on the lefthand face of plate portion 80 radially outwardlyfrom valve seat 90, for cooperation with an annular valve 96. A furtherannular valve seat 98 is also formed on the left-hand face of plateportion 80 at a greater radius than that of valve seat 94,valve seat 98cooperating with annular valve 100.

In the illustrated arrangement, valves 92 and 96 are formed integrally,as of rubber, that integral element having one or more air passageways102 therethrough adjacent valve 92, and further having a base flange 104provided with one or more perforations accepting one or more pins 106projecting from the base of a piston or carrier 108 which may be ofplastic. Those same pins-106 also engage perforations in an annular baseportion 110 of a second integral rubber member which also includes theflap (or lip) type annular valve 100. The two integral rubber membersare secured to the carrier 108, as by means of retaining rings.

Carrier 108 is further provided with a central air passageway 112,aligned with valve 92, and a radial notchtype orifice 114 extendingtherefrom. A spring washer 116 acts between carrier 108 and valve 92,tending to force valve 92 to the right away from the carrier 108. Acompression spring 118 operates between the lefthand face of carrier 108and a base plate 120 which is secured to the body 50.

The function of the just-described subassembly including valve 92 isthat of pilot valve to sense changes in the intake 'manifold pressure ofthe engine with which this system is associated and to operate inresponse to preselected changes of that intake manifold pressure tochange the pressure in chamber 56 in a manner to produce desiredmovement of movable wall or diaphragm 44 so as to control valve 30. Thefunction of physically moving valve 30 is performed by diaphragm 44,separately from the intake-manifoldpressure sensing function, and thefunction of timing the duration of the opening of valve 30 is alsoperformed by apparatus including diaphragm 44 and orifice 68, ratherthan by the pilot valve assembly.

To permit sensing of the intake manifold pressure conditions, body 50 isprovided with an integral nipple 124 which is connected by a hose to theintake manifold of the internal combustion engine. That intake manifoldpressure is communicated through nipple 124, through a passageway 126 inbody 50, through one or more slots 128 in body 50, constitutingpassageways,"and to-the chamber 129 defined in part by base plate 120and carrier 108. That instant pressure condition is then communicated(by air flow in either direction) through passageway 112 and throughorifice 114 to the chamber 130 which is defined in part by valve 100,body 50, and valve 92. It will be observed that those instant pressureconditions will also be communicated through passageway 126 to thevolume 132 adjacent the outer surface of the annular valve 100.

Body 50 is further provided with an air passageway 134 connected toatmosphere and communicating with a chamber 136 which includes the innerfaces of the annular valves 100 and 96. Accordingly, when the vehicle isbeing driven at a steady condition down the road, so that the intakemanifold pressure is not significantly varying, a pressure differentialexists across flap valve 100 tending to maintain it in seated engagementwith -valve seat 98, and a pressure differential exists across flapvalve 96 tending to keep it seated against seat 94.

In addition to the opening force resulting from the fact that valve 92is exposed to above atmospheric pressure through passageway 84, thepilot valve assembly (also including piston 108) is also subjected tothe air pressure conditions in chambers 129 and 130. The effective areaagainst which the effect of the below atmospheric pressure in chamber130 is exerted is substantially less than the effective area againstwhich the pressure in chamber 129 is exerted and that difference is in asense to tend to open the pilot valve assembly. However, spring 118 isselected at a value to maintain the valves closed under relativelysteady state intakemanifold vacuum conditions. As an example, thatspring may exert a force of pounds in a design in which the effectivearea operated on by the pressure in chamber 130 is 0.3 square inches andin which the effective area operated upon by the pressure in chamber 129is 0.8 square inches.

With gradual changes in the intake manifold pressure of the vehicle, thepressures in chambers 129 and 130 adequately rapidly equalize, due tothe flow of air through orifice 114, and the pilot valve remains in theillustrated condition. The pilot valve will not be responsive to a rapidincrease in the absolute pressure of the intake manifold since that willcreate, transiently, a greater pressure in chamber 129 acting on thelarger valve area, and hence tending to keep valve 92 closed. However,upon an abrupt decrease in the absolute pressure of the intake manifold,the pressure in chamber 129 will transiently drop substantially belowthe pressure in chamber 130 (since the rate of pressureequalizing airflow through orifice 114 is small), creating a pressure differentialtending to open valve 92. If the magnitude of that pressure differentialis adequate, in the light of the other forces acting upon the pilotvalve system as above discussed, pilot valve 92 pops open. As thatoccurs, the positive pressure in chamber 56 prompts the flow of airthrough passageway 84 to increase the pressure in chamber 130, so as toincrease the instant pressure differential tending to hold valve 92open. Thus, valve 92 in effect acts regeneratively, the partial openingof that valve creating forces tending to fully open that valve. Thus,orifice 114 needs only to be small enough to delay the application intochamber 130 of the reduction of vacuum which occurs in chamber 129 longenough for pilot valve 92 to crack and regeneratively pop open.

The function of valve 92 is to rapidly reduce the pressure in chamber 56so as to prompt the diverter valve to perform its function. To this end,when valve 92 opens, the positive pressure in chamber 56 (as it nowappears in chamber 130) establishes a pressure differential across theflap valve 96 in a sense to separate flap valve 96 from valve seat 94 sothat the positive pressure in chamber 56 will produce flow of airthrough chamber 130 and past valve 96 to atmosphere through passageway134. Further, when the pilot valve assembly including carrier 108 popsto the left under the critical sensed condition, spring 116 is freed toforce valve 92 away from rubber member 108 by a small amount. Thiseffectively opens orifice 1 14, creating a circumferential enlargementof that orifice. As a result, the air pressure in chambers 56 and 130produces a flow of air through the now-enlarged orifice 114 (which actsin effect as a low-impedance passageway under this condition), throughpassageway 112, and to the intake manifold through nipple 124. Theseconjoint outflow paths for the air under pressure in chamber 56 coexistuntil that air pressure reaches substantially atmospheric value. As soonas the pressure differential between chamber 130 and chamber 136 reducessubstantially to zero,

flapper valve 96 again closes and closes off the connection toatmosphere via passageway 134. Accordingly, the pressure in chamber 56can be drawn below atmospheric value via the path including thenow-enlarged orifice 114. In the preferred embodiment of the invention,the pressure in chamber 56 is reduced below atmospheric pressure toincrease the pressure change during timed restoration of valve 30.

While the rate of opening movement of valve 30 can be selected asdesired, in the preferred embodiment the restrictive effect of orifice114 is reduced to a very small value so that the reduction in pressurein chamber 56 can occur quite rapidly, preferably in a fraction of asecond.

During a portion of the interval in which the pressure in chamber 56 isbeing reduced, there will be an inflow of positive pressure air fromport 10 through passageway 64, orifice 68, and past valve seat 88.However, in the preferred arrangement, the impedance to air flow fromchamber 56 via passageway 134 and, in parallel, via the now-enlargedorifice 114 is small relative to the impedance to air flow presented byorifice 68.

As soon as the pressure in chamber 56 reduces enough to overcome theclosing forces operating on diaphragm 44, diaphragm 44 and valve stem 32move to the left in view of FIG. 1. That movement is rapid and iscontrolled by the pressure in chamber 56. It continues until valve seat88 engages valve 86. That seating occurs when chamber 56 has beenreduced to a preselected pressure (in comparison with the pressure inchamber 54) which, in the preferred arrangement, is below atmosphericpressure but is above the intake manifold pressure, from one operationeven though the change in intake manifold pressure which for constancyproduced the operation of the pilot valve may vary from one operation tothe next. The engagement of valve 86 with valve seat 188 adequatelyseals the passageway 84 so that pilot valve 92 snaps closed, the rate offlow of air through orifice 68 (and 104) being too low to preclude thatoccurring.

The distance between valve seat 88 and valve 86 effectively determinesthe stroke of valve 30 which may be, as an example, one quarter of aninch. if the change in pressure of the intake manifold is such as tocreate the forces to open valve 92, the preferred system is designed sothat this full-stroke movement of valve 30 will occur, that is, thesystem desirably provides full-stroke movement of valve 30 in responseto any of the variety of abrupt changes of the intake-manifold-pressureconditions which should produce air diversion, rather than varying thestroke with variations in those abrupt changes of intake manifoldpressure.

While, as above noted, the engagement between valve 86 and valve seat 88adequately reduces air flow through passageway 84 to permit restorationof the pilot valve, the seal is not perfect, for a nick or other orificemeans is purposely formed in the valve seat 88. As a result, withchamber 56 now below atmospheric pressure due to the above-notedtransient operation of pilot valve 92, and with valve 86 in engagementwith valve seat 88, and with port 10 at or above atmospheric pressure,air will flow through passageway 64, through cavity 66, through orifice68, through nick 140 into chamber 56 to start to increase the pressurein chamber 56. As soon as the pressure in chamber 56 commences to rise,diaphragm 44 and hence valve stem 32 commence to move to the right inthe view of FIG.

l, separating valve 86 from valve seat 88, which eliminates the orificeeffects of nick 140 and establishes calibrated orifice 68 as thecontroller of the rate of air inflow. As the pressure in chamber 56approaches equality with the pressure in chamber 54, the valve becomesrestored to the closed position as illustrated in FIG. 1 of thedrawings.

Since, as above noted, the pressure in chamber 56 is reduced effectivelyto a constant value (in relation to the pressure in chamber 54) at eachoperation of the pilot valve 92 and since calibrated orifice 68 controlsthe rate of inflow of air into chamber 56, the delay in the reclosure ofvalve 30 to valve seat 26 can be essentially constant from one operationto the next, and among mass-produced valves.

The critical change of condition of theintake manifold pressure whichprompts actuation of the pilot valve may be selected in accordance withthe automobile manufacturers needs. The controlling factor is the forcetending to close pilot valve 92. Whenever that instant force (resultingfrom the pressures operating on different areas) is sufficient toovercome spring 118, pilot valve 92 will pop open. FIG. 2 illustratessome of those conditions. Curve 150, which is a plot of intake manifoldvacuum against time, illustrates a representative condition in which theintake manifold vacuum has stabilized at about 7 inches of mercury andthen (due, for example, to the driver removing his foot from theaccelerator pedal) abruptly changes in a short time to a vacuum of about19 inches of mercury. Curve 152 illustrates another common condition inwhich the intake manifold vacuum abruptly changes from just over inchesof mercury to just under 25 inches of mercury. Curve 154 representsanother example in which the intake manifold vacuum abruptly changesfrom a value of about 2 inches of mercury to a value of about 16 inchesof mercury. Under each of those conditions, in the representativesystem, the valve 30 should be abruptly opened and slowly closed toestablish a time delay adequate to permit the transient anddangerouscondition to dissipate. The physical movement of valve 30 from its 0" orclosed position is illustrated by curve 156 in FIG. 2. In thatrepresentative curve, valve 30 moves from its fully closed position toits fully opened position (representativelyone quarter of an inch) inless than one-half a second and then slowly closes, not becomingfullyclosed until about 6 seconds after its opening movement wasinitiated. The consistency of operation of which the valve is capable isreflected in the presentation of but one curve 156 common to each of thecurves 150, 152 and 154.

In the condition illustrated in FIG. 3, the intake manifold changesabruptly from a value of about 2 inches of mercury to a value of aboutl4 inches of mercury, a sensed condition which, in the assumed systemwith which the apparatus is associated, should not produce divertingmovement of valve 30. With an appropriately designed valve of the typeillustrated, that illustrated change will not produce diversion. Thedifference between curve 158 and the curves 150, 152, and 154illustrates the capability of the disclosed valve to accurately respondwhen it should respond and to not respond when it should not respond.

The pilot valve system including valve 92, thus far described, servesthe function of actuating (via diaphragm 44) valve 30 through a timedcycle from closed to open to closed in response to an abrupt change ofthe intake manifold pressure of a preselected degree and betweenpreselected ranges. That cycle of operation occurs in a preselected timeperiod, which, with the noted design, may be constant or effectivelyconstant, if desired, despite variations of the sensed conditions withinthose ranges of variation.

In some applications, it may also be desirable to reduce the magnitudeof the air flow through the utilization system in response to otherintake manifold conditions which are not or need not be transient.

Thus, with some utilization devices and particularly with some catalyticconverters, it is or may prove desirable to reduce the magnitude of airflow during continuing low intake manifold vacuum conditions, eitherabruptly (that is, an abrupt reduction to a preselected value) or on aprogressive basis (that is, a progressive reduction in the rate of flowas a function of the magnitude of the reduction of the intake manifoldvacuum below a preselected value). Correlative considerations may applywith continuing high intake manifold vacuum conditions.

An example is illustrated in FIG. 5 of the drawings, which is a plot ofair flow through port 20 (of FIG. 1) versus intake manifold vacuum. Thenormal air flow (with valve 30 fully closed) is illustrated byhorizontal portion of the curve of FIG. 5. In the representative systemreflected by the curve of FIG. 5, at an engine vacuum of about 5 inchesof mercury, the rate of air flow through port 20 is progressively orproportionately reduced, as illustrated by curve portion 172, reachingzero flow (that is valve 30 fully open) at approximately three inches ofmercury intake manifold vacuum. Similarly, portion 174 of the curve ofFIG. 5 indicates a representative reduction of the air flow through port20 in response to an intake manifold vacuum of a high value, the airflow commencing to reduce at about 18 inches of mercury vacuum, andprogressively and proportionally decreasing as the intake manifoldvacuum rises above that figure. Both curve portions 172 and 174 arepurely representative in their point of institution and their slopes mayreadily be changed by those skilled in the art.

In the illustrated embodiment of the invention, the means for producingportion 172 of the curve of FIG. 5 includes a valve 176, which may be ofrubber, cooperating with a valve seat 178 formed integrally with body 50and surrounding a port 180. Valve 176 is an enlarged integral element ofa diaphragm 182, the peripheral bead of which is trapped in an annularcavity 184 in body 50 by a plate 186 which is apertured at 188 to exposethe upper surface of diaphragm 192 to atmospheric pressure.

A reinforcing plate 190 which may be of rigid plastic or metal, isembedded in an annular slot in valve 176 and underlies diaphragm 182 toprevent the collapse of that diaphragm which could otherwise occur withthe upper side of the diaphragm being at atmospheric pressure and thelower side being occasionally subjected to high intake manifold vacuums.A compression spring 192 operates between a seat on body 50 andreinforcing plate 190.

Chamber 194, to which the underside of the major portion of diaphragm182v is exposed, is essentially at intake manifold pressure in view ofthe direct connection of that chamber to intake manifold through nipple124. Accordingly, when the vehicle is operating, atmospheric pressure atthe upper surface of diaphragm 182 tends to force valve 176 into sealingengagement with valve seat 178, spring 192 tends to open the valve, thepositive pressure in chamber 56, operating on the under surface of valve176 within valve seat 178, tends to open the valve, and the vacuum inchamber 194 tends to close the valve 176. Balance of these conditionsmay be selected at any suitable value, such as the above indicatedinches of mercury vacuum in the intake manifold. When the intakemanifold vacuum is higher than that value, valve 176 will remaincontinuously closed and will perform no function in the operation of thesystem. As the intake manifold vacuum decreases below that value (thatis moves toward its atmospheric value) valve 176 is separated from seat178, permitting the air under positive pressure in chamber 56 to escape(at a controlled maximum rate) through orifice 180, through the orificecreated by the variable separation of valve 176 from seat 178, and tothe intake manifold through nipple 124. Valve 176 operatesdegeneratively so that it does not tend to pop open in response to thiscondition. As a result, a fluid-dynamic condition exists with airflowing from the pressure in port through passageway 64, orifice 68,chamber 56, orifice 180, valve 176, and the intake manifold, toselectively reduce the absolute pressure in chamber 56 so as toestablish a new position for diaphragm 44 and hence a new relationshipbetween valve 30 and valve seat 26, partially opening that valve as afunction of the reduction in intake manifold vacuum below thepreselected value. A representative relationship is illustrated inportion 172 of the curve of FIG. 5. If it is desired to increase theslope of portion 172, valve seat 178 can be made smaller; while if it isdesired to decrease the slope of portion 172, the valve seat 178 can bemade larger. The point of initiation of the portion 172 of the curve ofFIG. 5 can be controlled, for example, by selection of spring 192.

If it is desired to reduce the rate of air flow at high intake manifoldvacuums, in the pattern of portion 174 of the curve of FIG. 5 (or someother pattern), this may be accomplished, as an illustrative example,with a mechanism such as that shown in FIG. 1A of the drawings, usedalternatively to the mechanism including valve 176 in FIG. 1 of thedrawings or, if both portions 172 and 174 are desired, supplementary tothe mechanism including valve 176, by disposing the mechanism of FIG. 1at some other circumferential point on the body 50.

The mechanism of FIG. 1A includes a valve 200, made, for example, ofrubber, which is integral with a diaphragm 202, the peripheral head ofwhich is suitably clamped to the body 50 by means including a clampingring 204 and a clamping plate 206. A spring 208, operating between plate206 and valve 200, forces valve 200 into sealing engagement with a valveseat 210, which defines a passageway 212 communicating with the chamber56. Since the valve 200 is spring biased closed, it is not essentialthat the communication between the valve seat 210 and chamber 56 includea restriction or orifice correlative to orifice 180 in FIG. 1. Thevolume above diaphragm 202, which is a part of chamber 194, is at intakemanifold pressure, and chamber 214, below diaphragm 202, is incommunication through passageway 126a, with the intake manifold pressureof the engine via nipple or fitting 124 (FIG. 1). The pressure inchamber 56 tends to open valve 200, operating on an area thereof throughvalve seat 210.

Intake manifold pressure in chamber 214 tends to close valve 200, intakemanifold pressure in the chamber above diaphragm 202 tends to open thevalve 200, and spring 208 tends to close that valve. Spring 208 isselected to maintain valve 200 closed until a preselected pressure isreached such as the approximately 18 inches of vacuum illustrated inFIG. 5 of the drawing of the initiation of curve portion 174. When theintake manifold vacuum exceeds the preselected amount (that is, when theabsolute pressure sufficiently reduces), valve 200 commences to open,operates degeneratively and modulates the outflow of air from chamber 56in a manner to progressively translate valve 30 away from engagementwith valve 26 (FIG. 1) to reduce the effective rate of air flow via port20 to the utilization system, pursuant to the pattern of curve 174 inFIG. 5. Again, the initiation point of that curve can be selected asrequirements dictate and the slope of that curve can be adjusted byutilizing the principles previously noted.

In the valve system illustrated in FIG. 1 of the drawings, chamber 56 isnormally at a pressure above atmospheric pressure and the reduction ofthat pressure produces either an abrupt or a progressive translation ofthe valve 30 away from engagement with valve seat 26 in accordance withthe nature of that signal. The fact that chamber 56 is at a positivepressure and that valve 30 can be translated in response to reduction inthat air pressure permits the valve system of FIG. 1 of the drawings toserve a further function. Thus, in a postcombustion system in whichthere is supplemental burning of the emission products of an engine,safety requirements may dictate that the auxiliary combustion chambernot be supplied with oxygen at a rate which will create a dangerousovertemperature condition in that combustion chamber, whether thatcombustion chamber be a catalytic converter, such as the unit 22representatively illustrated in FIG. 1 of the drawings, or some otherunit. If such overtemperature conditions are sensed, means shoulddesirably be provided to terminate that condition, which requires bothsensing of the overtemperature condition and effective control of theair flow in response thereto. In the illustrated system, this isaccomplished by providing a senser 216, mounted in the casing 214 of thecatalytic converter 22 (or other post-combustion device) to sense theexistence of a critical over-temperature condition therein. Senser 216may comprise a cup element 218 projecting within casing 214 so as to beexposed to a critical internal temperature. A tube 220 projects withinthe cup 218. Tube 220, in the illustrative embodiment, is connected by asuitable hose to a nipple 222 formed in body the passageway throughwhich communicates through one or more notched passageways 58 withchamber 56. Tube 220 may be supported in cavity 218, as an example, by acover 224 which engages both the cup 218 and the tube 220 and which hasa passageway 227 therethrough extending to atmosphere. Cup 218 may beceramic and tube 220 and cover 224 may be of stainless steel. However,if corrosion problems are serious, as they may well be in a givenutilization of the principles of this system, both cover 224 and tube220 may also be ceramic, if desired, or other suitable heat andcorrosion resistant materials.

Cup or pot 218 is substantially filled with, and tube 220 is sealinglyembedded in, a substance 226 which has the characteristic that it issolid (andeffectively seals tube 220) at any temperature below thatpreselected' critical temperature, but is liquid thereabove. It shouldfurther have the characteristic of having a suitable pressure head whilemolten, with a feasible distance between the lower end of tube 220 andthe upper surface of the substance 226.

Below the aforesaid critical temperature, substance 226 is solid andeffectively seals tube 220 so that no air can flow from chamber 56through tube 220, and the valve system of FIG. 1 operates precisely asdescribed. During that normal operation, chamber 56 of the valve systemcontinues to remain at an above-atmospheric pressure condition. If,during that operation, so much air flows through the catalytic converter214, or other such device, as to create a critical overtemperaturecondition, heat is transferred through cup 218 to the substrate 226, tomelt that substance. Upon becoming molten, it no longer totally sealstube 220 and air under pressure in chamber 56 flows through nipple 222,through a check valve 230, to the tube 220. This pressure is positiverelative to atmosphere and as a result the pressure in tube 220 willbubble air through the now-molten substance 226, that air escaping toatmosphere through passageway 226. That bubbling will occur at whateverrate is necessary to maintain the pressure in pipe 220 (above the moltensubstance) at a value equal to the head of the molten substance betweenthe lower end of the tube 220 and the surface of that molten substance.This pressure is selected to be less (by selecting the characteristicsof the substance and the extent of submersion of the tube 220 therein)at a value such that it will produce a reduction in the pressure of thechamber 56 sufficient to cause diaphragm 44 to move valve 30 to the leftto divert the air from port to port 24 sufficiently to reduce (to zeroif desired) the rate of outflow through port to the utilization systemenough to reduce the temperature of the utilization system (such as thecatalytic converter 214) below the critical value. When that occurs, thesubstance 226 will resolidify, to terminate the bubbling and toeffectively block the tube 220 so that chamber 56 will restore to thepressure condition at which valve is closed. I

The temperature at which the substance 226 should melt, so as to causevalve 30 to be opened to divert the pump air flow, will, of course, varywith different utilization systems, and should be selected to match theovertemperature requirements of each such system. Any of a variety ofsubstances may be employed providing they change from a solid to aliquid state at the desired temperature, pass bubbles'of air while intheir liquid state, do not burn or excessively oxidize under conditionsof use and are otherwise generally suitable. Salts, such as alkali metalsalts, are suggested, including those which have been used in the heattreating of metals, including the chlorides and nitrates of potassium,barium and sodium, and mixtures thereof, establishing various criticalmelting temperatures. Sodium chloride, for example, has a nominalmelting temperature of l,472F which may well be acceptable withcertaincatalytic converters. Materials other than inorganic salts may,of course, be employed. As an example, an alloy of 67 percent copper and33 percent tin melts at a nominal temperature of l,365F. As anotherexample, if the critical temperature is higher (as it may well be,particularly with non-catalytic postcombustion devices), copper, nickel,and alloys thereof generally have higher melting points and can serve asthe selected substance.

Substance 226 should be in a solid form (desirably not granulated) inthe senser cavity as by casting the molten material in place in cup 218,(by heating it in situ, or heating it remotely and pouring it into thecavity while molten), or precasting appropriately shaped pellets of thematerial, the former being presently preferred in view of the ease ofestablishing a sealing relationship with tube 220.

While those skilled in the art will recognize the disadvantages of sucharrangements, they will perceive that the change of state of thesubstance 226 which is sensed upon the attainment of the preselectedtemperature could be either a sublimation or a change from the liquid tothe gaseous state of the substance. It is also contemplated that senser216 could comprise a pair of stationary, spaced electrical electrodes(such as a pair of spaced-apart rods embedded in the substance, or asingle electrode embedded in the substance with a metallic' pot 218constituting the second electrode) which, with associated knowncircuitry, would detect the change in resistance (or capacitance) as thesubstance 226 changes from a solid to a liquid state or from a liquid toa gaseous state, and it is further contemplated that the senser 216could comprise a pair of electrical contacts (of which a metallic pot218 could be one) which are held apart by the substance 226 when solidand are permitted to engage when substance 226 melts, coupled withcircuitry for detecting the fact of closure and apparatus (such as asolenoid) to repetitively momentarily restore-the contacts so that theywill be separated when the substance 226 resolidifies. It is alsocontemplated that the pot 218 may be capped with a diaphragm (orbellows), such as stainless steel, in lieu of the tube 220, with thatdiaphragm being spaced above the substance 226 and carrying, on itsupper surface, an electrical contact matable, upon adequate deflectionof the diaphragm, with a second electrical contact to establish anelectrical signal reflecting an overtemperature condition, with thediaphragm being deflected to that critical extent in response to anincrease of the vapor pressure of the substance 226 which occurs eitherwhen a given substance changes from the solid to the liquid state, or isadequately heated after such conversion, or converts from the liquid tothe gaseous state, or is adequately heated after such conversion.However, those arrangements are believed to be greatly inferior to thepreferred arrangement disclosed.

The curve of FIG. 4 reflects a suitable relationship between the rate ofair flow to the utilization system via port 20 and the temperaturesensed by the senser 216. It is assumed, in the curve, that thepreselected critical temperature of the catalytic converter 214 whichshould not be exceeded is about 1,472", it being recognized that anygiven commercial unit may well require significantly differentoperational temperature limitations. Accordingly, the substance 226 inthe senser may be selected as sodium chloride. In the portion of thecurve 236, full air flow is produced, that is, valve 30 is fully closed.At about 1,472F, substance 226 melts, the pressure in chamber 56 isreduced due to the bubbling through the now-molten substance 226 andvalve 30 is opened, to change the rate of air flow via output port 20along the portion 238 of the curve of FIG. 4. It will be appreciatedthat the reduction in air flow can be in effect modulated, if desired,in a commercial installation so as to produce a certain reduction in theair supply to the auxiliary combustion device when that device reaches afirst preselected temperature, and then further reducing the air flowif, but only if, the temperature of the device continues to rise(despite the reduction in air flow) and attains a second highertemperature, as indicated in the dotted line curve 240 in FIG. 5. It iscontemplated that this can be accomplished by utilizing two sensers 216with their tubes 220 connected in parallel to the nipple 221 and withthe substances 226 in the two sensors being selected to have the desireddifferences in melting points.

While the high temperature senser has been illustrated in combinationwith a valve having a control chamber which is normally aboveatmospheric pressure, with reduction of the pressure in that chambertowards atmospheric pressure producing movement of the valve in adirection to divert the pump air from the utilization system, it will beappreciated that the principles can also be applied to other types ofvalve systems including valves operating at other pressures, (above orbelow atmosphere) or in which an increase in absolute pressure isrequired to produce diverting action. For example, pipe 220 can beopened directly to atmosphere, and port 226 can be connected via acounterpart of nipple 222 to a valve chamber which is normally belowatmospheric pressure and which will cause the valve to divert the pumpair flow in response to an increase in absolute pressure. As anotherexample, a source of positive absolute pressure can be connected to pipe220, with port 226 being connected to a valve chamber which is belowthat positive pressure and which causes the valve to divert the pump airin response to an increase in absolute pressure. As a further example,port 226 can be connected to a source of negative (below atmospheric)pressure, with tube 220 being connected to a valve chamber which is at ahigher absolute pressure and which produces diverting movement of thevalve 30 in response to a reduction in that absolute pressure. In eachcase, it is desirable, of course, that the direction of air flow throughthe senser be downward (in the sense of the view of FIG. 1) through tube220. The sensor 22 can also be employed to actuate a different type ofair-pressure or air-flow responsive device which in turn controls theactuation of a different type of diverter valve. As an example, apressure-sensitive electrical switch (responsive to the change ofpressure which results when the temperature sensitive material becomesmolten) can be used to control a solenoid-controlled diverter valve.Other utilizations of the principle will be apparent to those skilled inthe art to whom this disclosure is directed. The disclosed system isthat presently preferred.

If it is desired to signal the existence of the overtemperaturecondition, to warn the diverter, the apparatus 230-233 may be added tothe system of FIG. 1. Check valve 230, having a low forward pressuredrop, is inserted in sensers between nipple 222 and tube220. When thesystem of FIG. 1 is placed in operation, the positive pressure inchamber 56 will be communicated to tube 220 via valve 230. While duringsubsequent use, chamber 56 may, have the pressure therein reduced duringthe operation of other elements of the system, in the absence of anundertemperature condition, check valve 230 will preclude the pressurein the line leading to tube 220 from reducing below thatabove-atmospheric value. That above-atmospheric pressure is communicatedto the pressure switch 231, of any well known conventional type whichincludes a pair of contacts which are held open in response to positivepressure and which close only in response to the reduction of thatpressure. Accordingly, in the absence of a sensed overtemperaturecondition, pressure switch 231 maintains its contacts open. Thosecontacts are in series with a battery 232 and a warning light 233 and,since they are open, warning light 233 remains extinguished. If, duringthe operation of the system, an over temperature condition exists,substance 226 becomes molten and air is bubbled from chamber 56 throughthat molten substance to atmosphere, and the pressure in the line to theleft (FIG. 1) of check valve 230 reduces. This reduction in pressure issensed by pressure switch 231 which thereupon closes its contacts toenergize warning light 233. This warning light continues not only untilthe overtemperature condition has been alleviated so that substance 226is solidified, but also thereafter until chamber 56 restores to apositive pressure, which is communicated through check valve 230 topressure switch 231 to actuate it to open its contacts and extinguishwarning light 233.

The modified diverter valve of FIG. 8 of the drawings is similar, inrespects, to that disclosed in FIG. 1 and elements performingcounterpart functions are similarly designated. The valve of FIG. 8differs primarily in that the motive force is derived from intakemanifold rather than from pump pressure, the sensing and timingfunctions are not divorced and certain of the additional capabilities ofthe valve of FIG. 1 have not been disclosed in the drawing of FIG. 8.

In general, the valve assembly of FIG. 8 includes a valve 30' carried bya valve stem 32' driven by a diaphragm 44' clamped between washers 46'and 48', that assembly being biased to the right by a spring 60'disposed in a cavity 56' which is directly connected to the intakemanifold through nipple 124. Cavity 54' to the right of diaphragm 44',is connected to cavity 56 through tapered hole 66 in valve stem 32,calibrated orifice 68', and passageway 64, cavity 54' further includinga cavity portion 250 connected therewith by a plurality of passageways252 formed in a support member 254, which is supported by element 52'.Cavity portion 250 further being in communication with cavity portion256 by means of a passageway 258 formed in washer 46'.

The annular end of support member 254 sealingly engages the bead 262 ofa rolling lobe diaphragm 264, and the annular projecting end of a sleeve260 sealingly forces an inner bead 266 on that same diaphragm 264 intocircumferential cavity 268 formed in the valve stem 32', the other endof sleeve 260 bearing against, and centered on, washer 46'. As a result,rolling lobe diaphragm 264 establishes a sealing engagement with valvestem 32' and prevents the positive pump pressure which appears in port10' from entering chamber 54' around the valve stem.

At any given steady intake manifold vacuum both chambers 56' and 54'will be at the same pressures. While those pressures act upon differentareas, in accordance with the prior discussion of FIG. 1, spring 60'forces valve 30' closed under those equalized conditions.

In response to an abrupt increase in the intake manifold vacuum (asudden decrease in absolute pressure) of adequate magnitude and in anappropriate range, the instant reduction of pressure in chamber 56produces opening of valve 30'. Pressure equilibrium will be restored,and valve 30' will close, after a timed interval determined bycalibrated orifice 68'.

The temperature senser 216 of FIG. 1 may be associated, if desired, withthe valve of FIG. 8. Thus, as one example, a nipple 270 may be insertedin an aperture in housing element 12' so as to communicate with the pumppressure in port 10. Nipple 270 is provided with an orifice 272. Nipple270 is connected by suitable tubing to tube 220' of senser 216'. Anipple 274 is secured to the cap 224' of the senser 216' communicatingwith aperture 227'. A tube 276 connects nipple 274 both to a pressureswitch 231 and to a nipple 278 mounted in the cover 52' and hencecommunicating with chamber 54.

Pressure switch 231, conventionally consisting of a diaphragm, a spring,and a pair of electrical contacts, is designed to have its contacts openwhenever the pressure applied thereto, though tube 276, is belowatmospheric value and to close its contacts whenever the pressureapplied thereto is above atmospheric value. There is an advantage toadjusting the tolerances so that the switch contacts will be closed atatmospheric pressure for lamp proving purposes, although such is notessential. Pressure switch 231 may actuate a warning lamp similar towarning lamp 233 in FIG. 1, or perform any other signalling or controlfunction.

With the system in operation, pressure switch 231' will be subjected tothe below atmospheric pressure in chamber 54' since substance 226' issolid and blocks air flow. If an overtemperature conditionoccurs,substance 226' melts. At that time, air will flow from port',,nipple 170, orifice 272, pipe 220', will bubble through moltensubstance 226', and will then flow through nipple 274, tube 276, nipple278, and into chamber 54'. In the preferred arrangement, orifice 272 isselected, in the light of the other parameters of the 'system, so thatthe air flow will increase the pressure in chamber 54' (despite outflowof air chamber 54' through orifice 68 to intake manifold) to a valueabove atmospheric pressure. This increase in pressure in chamber 54willproduce divertingaction of valve 30' and will hold that valve in itsopen or diverting position as long as substance 226' remains'molten. Indesigning orifice 272, it must be appreciated that the pressure in port10' will reduce (although still remaining above atmospheric value) inresponse to the operation of valve 30'.

'The change in pressure in tubing 276 to a value above atmosphericpressure will actuate pressure switch 231', to prompt it to perform itssignalling (including alarm) or control functions.

When substance 226' solidifies, the noted air-flow path terminates andthe pressure in chambers 54' and 56' re-equalizes, through orifice 68,to reclose valve 30.

As a further illustration of the fact that the overtemperaturesignalling system may take other forms, a modification is shown in FIG.9 in which a tee 284 is secured to the projecting end of nipple 270",with the orifice 272" being mounted at the outer end of the tee. Theoutput of tee 284, through orifice 272", is passed through a check valve286 which desirably has a low forward pressure drop. The air flowingthrough the.

check valve is applied via tubing 288, to tube 220" of overtemperaturesenser 216". A pressure switch 231" is connected to tubing 288 so as tobe subjected to the pressure therein. Pressure switch 231", whichconventionally includes a diaphragm, a spring and a pair of contacts,should be of the type which maintains its contacts open in response to apressure above atmospheric value but should close its contacts when theapplied pressure drops to a value close to atmospheric (e.g.,l psigauge). Pressure switch 231" in turn controls a magnetically operatedvalve 290 of the type which conventionally includes a solenoid structureand an air valve. Air valve 290 is connected in series between nipple292 on tee 284 and nipple 278 on body 52".

When the vehicle is operating and the temperature of thecombustion'device is not abnormal, the positive pressure in port 10" iscommunicated through check valve 286 to pressure switch 231" to hold itscontacts open, and valve 290 blocks air flow between nipple 292 andnipple 278", and the valve of FIG. 8 operates normally. If the valve ofFIG. 8 diverts for some reason besides overtemperature conditions, thatpressure is maintained at pressure switch 231" by check valve 286.

If an overtemperature condition exists in the combustion device so thatsubstance 226" melts, the pressure applied to switch 231" approachesatmospheric value, due to the pressure drop across orifice 272", causing231" to close its contacts and actuate valve 290 which will establish anair-flow connection between nipples 292 and 278 so as to apply positivepressure to chamber 54" to operate the diverter valve to its divertingposition. The pressure in chamber 54", under this condition, can becontrolled and selected, if desired, by insetting an orifice in nipple292 of a size selected in accordance with the other parameters of thesystem, including the effective size of calibrated orifice 68'.

When substance 226" resolidifies, at the termination of theovertemperature condition, bubbling through port 227" terminates,resulting in the application of the higher pressure to pressure switch231" to shut off valve 290, to cause the valve of FIG. 8 to reclose. Itwill be appreciated that pressure switch 231" may also serve other oradditional signalling or control functions, including the actuation of awarning light.

As above noted, the pot or cup 218 of the overtemperature senser ispreferably ceramic. In the arrangement as thus far described, theovertemperature condition, as sensed by the melting of the. meltablematerial, derives from heat transfer from the operating portions of thecatalytic converter, to the ceramic cup or pot 218 and thence to themeltable material. If desired, the sensing of the overtemperaturecondition of the operating portion of the converter can be accomplished,or supplemented, by simulation. Thus, effective sensing can beaccomplished by forming the cup or pot 218, or a portion thereof, tosimulate the operating elements of the catalytic converter, such as, forexample, manufacturing the cup of a ceramic with a porous surface, likethe converters porous surface, impregnated with the same catalyst usedinthe operating elements of the converter (such as a platinum salt). Inthat arrangement, the cup 218 itself serves as a tiny auxiliarycatalytic converter correlative to the operating element of the mainconverter, would be heated to the same degree as the main operatingelement and would effectively sense the heat generated by its owncatalytic converting operation (together with the ambient heat createdby the operation of the main catalytic converter).

In the system of FIG. 9, pressure switch 231" is actuated upon theattainment of an overtemperature condition to actuate a magneticallyoperated valve 290, and also, if desired, to actuate a warning light.The actuation of valve 290 actuates the diverter valve to terminate orreduce the flow of fresh air from the pump to the catalytic converter.In some circumstances, this will not relieve the overtemperaturecondition of the converter if the engine is malfunctioning. For example,if a spark plug is defective, there may be sufficient air introducedinto the converter from the engine, (through the exhaust manifold) tomaintain or extend the overheating condition of the converter eventhough the pump be diverted. FIG. illustrates how the sensing of theovertemperature condition (such as the actuation 231" in FIG. 9) can beused to operate a magnetically operable valve 291 to operate a bypass292 of the catalytic converter 221, as long as the overtemperaturecondition continues.

The addition of the bypass and the bypass control equipment of courseentails expense to the public, and to the degree that it serves only, orprimarily, the function of preventing destruction of the catalyticconverter as a result of the occasional negligent driver continuing tooperate his car with a defective engine, the interest of the majority ofthe public might better be served by imposing upon the operator (ratherthan the car company and hence the rest of the buying public) the burdenof paying for the replacement of the catalytic converter if it isdestroyed as a result of his negligent failure to porperly maintain hisengine. In the arrangement of FIG. 11, the pressure switch 231' is alsoutilized to actuate a warning light 293 exposed to the driver's view, ason the instrument panel and to signal him that he should immediatelyshut off the engine and permit the catalytic converter to cool. FIG. 11also discloses a counter 294 (which may be buried in the automobile andsealed) which is stepped upon each actuation of pressure switch 231" toprovide information to the dealer and car company as to whether thereplacement of the catalytic converter should fairly be a warrantyexpense or whether the driver permitted the overtemperature condition torepetitively occur without attending to it. FIG. 11 further discloses,as an addition or alternative, a timer 295 (which may also be buried inthe vehicle and sealed) which is actuated to measure time throughout theduration of each actuation of pressure switch 231 to reflect the totalamount of time that the catalytic converter was subjectedtoovertemperature conditions, for the same purpose. Either a counter or atimer may be actuated, of course, other than by a pressure switch, andin response to any means for signalling the existence of anovertemperature condition.

As previously discussed, a function of the subject valve, in itsillustrative utilization, is to selectively and temporarily reduce (orterminate) the fresh air flow through the catalytic converter (or otheremission reducing system) under vehicular operating conditions whichwould make it dangerous, damaging or unwise to continue to flow freshair through the converter at full volume. The vehicular operatingconditions are, essentially, engine operating conditions and may be (andare in the illustrated arrangements) sensed by sensing the intakemanifold pressure of the engine and/or changes thereof. The valve servesto selectively and temporarily reduce the fresh air flow in response toan intakemanifold pressure condition or condition change constituting anindication that a reduction in air flow should be instituted. However,the relation between the intake manifold pressure (and changes thereof),and the condition decreeing a reduction in fresh air flow, changes withthe altitude (or elevation) of the vehicle as a result of the inherentcharacteristics of the engine. Accordingly, a preselected intakemanifold condition or change of condition accurately reflecting, at sealevel, a need to reduce air flow, will not accurately reflect that needat high altitudes, and vice versa. Hence, a diverter valve which isdesigned to respond to a certain intake manifold pressure condition orchange thereof will not produce proper diversion at both sea level andhigh altitudes. As an example, if a diverter valve is set to divert inresponse to a transient change in the intake manifold pressure of 15inches of mercury, so as to properly produce diverting action at sealevel, it will fail to divert, even though it should, at high altitudes,(such as 8,000 feet) simply because the requisite signal is not receivedfrom the intake manifold. If, to insure proper diversion and theavoidance of dangerous or damaging conditions at the higher altitude,the magnitude of the change of intake manifold pressure which signalsdiversion is reduced to 10 inches of mercury, then in normalpower-pattern driving at sea level at the diverter valve will tend tocycle (even though there is no condition requiring diversion) and thequality of emission control will be impaired.

Unless an acceptable compromise can be effected, the valve of FIG. 8,for example, is subject to that defeet. It is essentially solelyresponsive to intake manifold pressure and changes thereof. It has noeffective altitude compensating capability. While pump pressure doeschange with altitude, and while the valve of FIG. 8 is minorlyresponsive to pump pressure, the responsivity is in the wrong directionto compensate for the failure of the signal to accurately indicate theneed to reduce air flow over the range of altitudes, and in fact theresponsivity to pump pressure variations with altitude is in a directionto increase the erroneous operation of the valve with major altitudechanges.

The diverter valve should desirably be imbued with a capability tochange the character of the diverting action, with changes in vehiclealtitude, in a compensatory direction so as to produce proper divertingaction under all altitude conditions.

This can be accomplished by sensing altitude, as with a barometric typesenser, and utilizing that signal to modify the operation of thediverter valve. However, a simpler and more economic method ofeffectively sensing altitude is available in two forms. First, as abovenoted, the pump output pressure varies with altitude and the sensing ofthe pump pressure can provide an adequate sensing of altitude and thatsensing can be utilized to modify the operation of the diverter valve ina compensatory direction. Further, in a system in which the air flowfrom the pump is directed to the exhaust manifold of the engine so as tojoin with the exhaust emission in its flow to the catalytic converter,the exhaust manifold back pressure (particularly when the pump isdiverted) also signals and reflects the altitude of the vehicle, in itsrelation to intake manifold pressure. Either or obth of those signalscan be used to pro- In the system of FIG. 1, the pressure from the pumpis used as a motivating force for operating the valve. When the intakemanifold pressure or pressure change dictates operation of the pilotvalve to fully open valve 30, the duration of the fully open conditionand the time required for the valve 30 to move back to its illustratedclosed position will both be determined by the time required forsufficient air to flow through calibrated orifice 68 between chambers 54and 56 to establish the pressure difference conditions which will cause.

that reclosing of the valve, and the pressure in chamber 56, at thecommencement of that bleeding reflects an instant intake manifoldpressure, and the pressure in chamber 54 reflects the instant pumppressure. The direction of the change of pump pressure with altitude, asreflected in the pressure in chamber 54, is correct to cause the valveto compensate for those changes in intake manifold pressure withaltitude which cause the changeof intake manifold pressure to fail toaccurately indicate when diversion should occur.

The change of altitude, however sense d, can be employed to modify theinput intake-manifold pressure or pressure change which is required toproduce action of the diverter valve, can be employed to modify theduration of full opening of the diverter valve, can be used to modifythe time required for the valve to fully close once it commencesclosing, or a combination of any thereof.

The modified form of diverter shown in FIG. 12, il-' lustrates how thechanges of exhaust manifold back pressure, with altitude changes, can beeffectively utilized to cause the diverter valve to compensate for theduration of the fully opencondition of the valve is modified primarilyin response to intake manifold back pressure changes with altitude, andthe duration of the time required for the valve to move from its fullyopen to its fully closed position is modified, .to compensate foraltitude, primarily in response to the changes in pump pressure whichoccur with altitude. altitude changes, and also illustrates how thechanges in pumppressure, with altitude, can be utilized to cause thediverter valve to compensate for altitude changes. In the illustrativearrangement, toshow the capability to sense rhenmaiveaanaive (ifFIG?ffofthe drawings is similar, in respects, to that disclosed in FIG.1 and elements performing counterpart functions are in general similarlydesignated. Certain of the additional capabilities of the valve of FIG.1 have not been disclosed in the drawing of FIG. 12.

In general, the. valve assembly of FIG. 12 includesa valve 30"cooperating with valve seat 26" and carried .by a valve stem 32" whichis driven by a diaphragm 44" clamped between washers 48" and 46", thelatter of which serves asa deflector to shield-diaphragm 44" from directimpingement by hot gases. The described assembly is biased to the rightby spring 60 disposed in a cavity 56" disposed between the generallycupshaped body 50" (which may be made of plastic) and the diaphragm 44".

Body 50" is provided with a rightwardly extending projection 300 whichloosely slidably engages an enlarged cavity 302 in valve stem 32" toguide the latter in its reciprocatory movement along its longitudinalaxis during the operation of the device.

As in the system of FIG. 1, the valve is illustrated in associationwith, and includes, elements of a positive air pressure generatingsystem, such as a pump, having a pump outflow port 10 (connected to thepump) formed in a housing designated l2", 14'', 16' and 18", all ofwhich parts are normally integral and may be elements of the pumphousing itself or elements of the conduit in or to the pump. However, inFIG. 12 the outlet port 20" to the utilization system is laterallyoffset from the inflow port 10'. Cap 52" projects into the port 10" butthe port 62" is made much larger than in FIG. 1 to offer a lowrestriction to the flow of air from the pump, through the cavity 54",and out to the utilization system outlet 20" via an enlarged arcuateslot 304 formed in the wall of housing 52" in alignment with the outlet20". Port 304 is made sufficiently large as to offer a minimum impedanceto the flow of air from the pump and may in practice be long or more.

When the valve is in its illustrated position (which, since theillustrated valve is a diverting valve, may be termed the closedcondition), the'pump pressure, as it appears at inflow port 10'', alsoappears in chamber 54., and is also communicated through port 64", bore66", through calibrated orifice 68" and through the annulus between bore302 and guide projection 300 (which has no significant orificing effect)to cavity 56". As a result, in this steady-state condition, there iseffectively no pressure differential across diaphragm 44" and the valve30" is closed by the action of spring 60", operating between the body50" and the washer 48", aided by the pressure differential across valve30".

' When the valve 30" is opened (translated to the left) by an action tobe described, inflow port 10" is connected to return port 24". Inaddition, the left-hand annular face 308 of valve 30" adequately sealsagainst valve seat 306 on housing 52" so that valve 30" also effectivelyseals the pump'pressure from chamber 54". As a result, chamber 54-" iseffectively connected to the utilization system. That may be, asexamples, a direct connection to the exhaust manifold of the internalcombustion engine (with that manifold also being connected' to acatalytic converter), or such a connection through a volume check valveoperating in a direction to impede flow through port 20" in an upwardsense'in the view of FIG. 12, and readily permit flow in a downwardsense. It will be observed that under this fully open condition thevalve, inwhich valve surface 308 is effectively sealed to valve seat306,.pump pressure is no longer communicated to port 64" but rather thepressure in chamber 54" appears at port 64". Equalization of pressures(or pressure change toward equalization) between chambers 54" and 56"occurs (with flow in either direction, as appropriate) under the controlof the calibrated orifice 68".

The outer bead of an annular diaphragm 310 is trapped between the body50" and the cap 120", and the inner bead of that diaphragm is clamped tothe carrier 108". The carrier 108" is biased to the right by a spring118" acting against the end of cap 120". In the illustrated embodiment,nipple 124", secured to cap 120", is connected to the intake manifold ofthe engine. Pilot valve 92" cooperates with valve seat 90" to controlthe flow of air between chambers 56" and 130" via passageway 84". Valve90" is supported on a stem member 312 having a tapered or conicalsection 314 which passes through and cooperates with a bore 316centrally disposed in the carrier 108", bore 316 being desirably a fewthousandths larger in diameter than the largest diameter of the taperedsection 314 to permit passage of air therebetween under all conditions.Stem member 312 has a portion 318 which projects to the left through andis guided in an aperture in a tab 320 on the cap 120", tab 320 notsignificantly interfering with the flow of air between chamber 120" andnipple 124" A collar 322 is formed on stem member 312 a distance to theright of tab 320 (in the illustrated position of the apparatus) which isless than the distance between carrier 108" and the abuttable portion ofcap 120".

Under steady-state conditions, with the intake manifold at any constantpressure, that pressure appears in chamber 128" and is communicatedthrough the annular passageway between stem section 314 and bore 316,and then through the orifice 324 (which may be merely a nick or shallowgroove between carrier 108" and tapered valve section 326 of stem 312),and to chamber 130". Thus, under those steady-state conditions, thepressures in chambers 128" and 130" are equal and carrier 108" is forcedto the right, with a preselected force, by spring 118" to force valve 92into engagement with seat 90" so as to seal chamber 130" from chamber56'.

If there is an abrupt decrease (the degree of required abruptness beingselected by sizing orifice 324) in the absolute intake manifold pressureby an amount greater than the impeding force offered by spring 118", thetransient pressure differential between chambers 130" and 128" forcesthe carrier 108" and the valve 92' to the left. After valve 92" hasmoved adequately clear of valve seat 90", further leftward movement isstopped by the engagement between collar 322 and tab 320. Carrier 108"may, however, continue to move to the left an additional distance withthe effect of both opening orifice 324 and increasing the effectiveannular passageway between tapered portion 314 and bore 316, thetapering providing for modulation of the air flow and serving to preventexcess bleed to the intake manifold. By virtue of that air flow, andunder the assumed conditions, air in chamber 56" flows throughpassageway 84", past valve 92" into chamber 130", through the nowenlarged orifice 324, through the annulus between tapered section 314and bore 316, into chamber 128" and thence through nipple 124" to theintake manifold of the engine. The pressures in chambers 130" and 56"rapidly equalize through valve 92", and as soon as orifice 324 isopened, the pressures of both rapidly reduce (absolute) towards theinstant pressure in chamber 128". When the pressure differential betweenchambers 138 and 130" (and hence 56") reduces to a valve determined byspring 118", such as to inches, spring 118" forces carrier 108" to theright to reclose orifice 324 and pilot valve 92".

That abrupt reduction in the pressure in chamber 56" results in theestablishment of a pressure differential across diaphragm 44" in a senseto cause valve 30" to move from its closed to its diverting position,against the force of spring 50". Upon that event, and under the assumedconditions, air flows from chamber 54" through passageway 64", throughcalibrated orifice 68" and into chamber 56" to reduce the pressuredifferential on a time-delayed basis and when that pressure differentialadequately reduces, spring 60" again restores the valve 30" to itsillustrated closed position, the rate of restoration, after reclosingmovement commences, also being controlled by orifice 68'.

It will be observed that valve surface 308 of valve 30" is in engagementwith valve seat 306 during the diverting operation, chamber 54" isisolated or effectively isolated from the pressure from the pump (as itappears in port 10"), so that the pressure in chamber 54" (which affectsthe rate of change of the pressure difference between chambers 54" and56") reflects or varies as a function of the outlet pressure in port20". That outlet pressure does or can reflect the back pressure of theutilization device or system, and in the presented example, that outletpressure can or does relfect the exhaust manifold pressure of theinternal combustion engine. The exhaust manifold pressure of theinternal combustion engine in turn varies with or reflects the altitudeof the vehicle.

In effect, in the illustrated embodiment the apparatus derives apressure in chamber 56" (after the pilot valve has been opened) whichvaries as a function of the instant intake manifold pressure, derives apressure in chamber 54" which varies as a function of exhaust manifoldback pressure, and controls the duration of the full-open operation ofthe valve 30" as a function of that difference, with the change ofexhaust manifold back pressure, which occurs in response to an increaseof altitude, being used, in effect, to increase the time required forair to flow through orifice 68" sufficiently to change the pressure inchamber 56" to the value at which the forces are in balance so thatvalve 30" initiates its reclosing movement. At higher altitudes, theduration of the fully open condition of valve 30" is much longer thanthat occurring in response to the same intake-manifold-pressure-changesignal at sea level. Further, when valve 30" first starts to move backto the right to open the valve constituted by the engagement of surfaces308 and 306, the pressure in chamber 54" changes to the instant pressurein port 10" which also varies with variations in the altitude of thevehicle. From the time of that cracking of the valve 308-306 until valve30" is fully reclosed, the rate of air flow through orifice 68" will becontrolled by the difference in pressure between that pressure inchamber 54" and the pressure in chamber 56", so that the time requiredfor chamber 56" to reach a value at which valve 30" is fully reclosedwill also vary as a function of altitude, again, in a sense such thatthe time required for that closing movement to be completed at a highaltitude is greater than the time required for the full reclosure tooccur at sea level, in response to the sameintakemanifold-pressure-change signal. Thus, in the specific embodimentillustrated in FIG. 12, it is the total duration of the time frominitial opening of the valve 30" to full reclosing of valve 30" which iscompensatorily modified as a function of the altitude of the vehicle soas to produce proper diverting action effectively independently ofaltitude changes. Obviously, it is not essential that both the changesof exhaust back pressure with altitude and the changes of pump pressurebe effectively sensed or employed, nor essential that the total durationof the open time of valve 30 be adjusted in response to altitudechanges.

Those skilled in the art will best understand the operation of thepreferred embodiment by utilizing an example (in which all pressures arebut illustrative, and are given in inches of mercury, positive ornegative, in relation to sea-level atmospheric pressure).

In an illustrative arrangement, the effective area of diaphragm 310 was0.555 square inches, and the effective area of valve 90 was 0.025 squareinches, for a net area of 0.53 square inches. The effective area ofdiaphragm 44" was 0.71 square inches and the effective area of valve30", when closed as illustrated, was 0.40 squareinches for a neteffective area of 0.31 "square inches. When valve surface 308 is inengagement with seat 306, its effective area is 0.74 square incheswhich, in relation to the effective area of diaphragm 44", is a neteffective area of 0.03 square inches. Spring 118" has a force of 2.8pounds while that of spring 60" is 1.5 pounds.

As one example, assume that the intake manifold pressure in chamber128", and hence in chamber 130", is -15 inches, and that the pressure inport and hence in chamber 54" and chamber 56", is +8 inches. Under thatcondition, there will be a net force of 3.26 pounds closing valve 30"against valve seat 26". Those pressures are but illustrative, but areassumed to reflectthe conditions under road load at 50 mph at sea level.

If the driver, operating his vehicle at the above conditions at sealevel, opens the throttle to accelerate the engine to initiateacceleration of the vehicle, there will be an abrupt'rise in theabsolute intake manifold pressure and the increase in engine speed willalso increase the pump pressure in port 10". Assuming that the operatorhas opened the throttle enough to produce a change of the pressure inchambers 128" to 5 inches, the change is in the wrong direction to openpilot valve 92", but chamber 130" equalizes with chamber 128" throughorifice 324. Assuming also that under those conditions the pump pressurerises to +13 inches, with that pressure also existing in chambers 54"and 56", the net force will be 4.24 pounds, still in a closingdirection. Thus the valve 30" will remain closed, as illustrated.

Assuming that the operator then abruptly returns the throttle to aproper position to maintain road load at 50 miles an hour at sea level,the pressure in chamber 128" will promptly restore to the 15 inch value.If, as is here assumed, the valve is set to respond to an abrupt 10 inchchange in intake manifold pressure in the appropriate direction, pilotvalve 92 will operate because, at the time of the reduction of thepressure in chamber 128" to -1 5 inches, the pressure in chamber 130"was, as noted in the previous paragraph, 5 inches, resulting in apressure difference of the requisite 10 inches. As a result, carrier108" and valve 92" will travel to the left, and the pressure in chambers130" and 56" will become equal to one another and to a value of 10inches below the instant pressure in chamber 128", that is, in theassumed example, -5 inches, and pilot valve 92" will reclose. Sinceacceleration of'the engine is terminated, the pump pressure will haverestored to its initially assumed value of +8 inches and that also willbe the pressure in chamber 54". Under these conditions, there will be a13 inch pressure differential between chambers '54" and 56" and a netforce of 0.84 pounds in an opening direction, that is, in a direction tomove valve 30" to the left to terminate air flow to the utilizationsystem and divert the pressure from the pump to port 24". Of course,upon that diversion, the pressure at port 10" will reduce, such as to +2inches, as one example.

Because of the pressure differential between chambers 54 and 56", whichis 13 inches, air will flow from chamber 54" through calibrated orifice68" into chamber 56", the rate of that flow being a function of themagnitude of the pressure difference. At an interim point under theassumed conditions, when the pressure in chamber 56" has risen from theassumed 5 inches to 2.6 inches, the net force holding valve 30" in itsfully diverted position is zero and the pressure difference at thatinstant, between chambers 54" and 56" is 10.6 inches. Under the assumedconditions, the time required to reach that point of balance is veryshort. From that point on, the pressure in chamber "54" reflects thepressure at port 10" which also reflects altitude, and as air continuesto flow through calibrated orifice 68", valve 30 moves towards itsclosed position at a rate determined by the pressure difference and theparameters of the system. During this movement, the pressure at port 10"will rise (but still reflect altitude) as the valve closes, and thisrise will be communicated to chamber 54" since valve surface 308 isseparted from seat 306. It will be observed that when the pressure atport 10" rises to +4.3 inches, with that same pressure in chamber 54",and with the forces at balance, the pressure in chamber 56" will beatmospheric and the pressure difference between chambers 54" and 56"will be down to 4.3 inches.

Under the foregoing conditions, the total period of diverting actionwill be very short. For example, under the illustrative conditionspresented, the valve will re-, main fully open for less than one-halfsecond and will require about 1% seconds to move from its open to itsfully closed position.

Under correlative operating conditions, but at 8,000 feet, with thechanges in exhaust manifold back pressure and pump pressure reflectingthat altitude, valve 30" will remain fully open for a substantiallylonger period, such as about 2 seconds and, illustrating the effect ofsensing the change of pump pressure which occurs with altitutde change,the time required for the valve to move from its open position to itsfully closed position will also be longer such as, for example, 2%seconds.

This capability of compensating the overall system for changes inaltitude, does not adversely affect the capability of the system toproperly perform in response to varying intake manifold signals at aconstant altitude. As an example, if there is an abrupt change (at sealevel) of the intake manifold pressure in the correct direction and byan amount exceeding a preselected amount, the time that the valve isfully open and the time required for it to translate back to a fullyclosed position will be effectively constant independently of whetherthe change exceeds the preselected amount by just a bit or by asignificantly larger amount.

It will also be appreciated that the arrangement of FIG. 12 is butrepresentative, and shows the presently preferred way of varying theoperation of the valve as a function of altitude. It is alsocontemplated that the fact of diversion rather than the duration ofdiversion may be controlled as a function of altitude. It is alsocontemplated that altitude could be sensed either directly or by sensingexhaust manifold back pressure or by sensing pump pressure, or acombination thereof, and employed to control a modulating valve forcontrollng the effective size of the bleed orifice 68". It is alsocontemplated that the principles herein disclosed, or any of them, beused in valves for use in a bypass control arrangement, such as insubstitution for valve 291 in FIG. 10, or in other control applications.

What is claimed is:

l. A diverter valve system for selectively diverting the air outflow ofa positive output pressure air pump from a utilization system to adiversion system comprising first and second chambers divided by amovable wall which moves under the control of the air pressuredifferential between said chambers, a diverter valve controlled by saidmovable wall, means connecting said first chamber to said pressure fromthe pump, means including an orifice for connecting said second chamberto said pressure from the pump, and means for selectively momentarilyreducing the air pressure in said second chamber, said momentaryreduction of the air pressure in said second chamber producing movementof said movable wall in one sense, said movable wall moving in theopposite sense following said momentary reduction of the air pressure insaid second chamber under the control of said means including an orificefor connecting said second chamber to said pressure from the pump.

2. The combination of claim 1, in which said diverter valve, inoperation, diverts the air from the pump to atmosphere.

3. The combination of claim 1, in which said diverter valve diverts theair from the pump to the input to the pump.

4. The combination of claim 1, in which said diverter valve system isassociated with an automotive engine having an intake manifold and inwhich said means for selectively momentarily reducing the air pressurein said second chamber comprises separate valve means connected to theintake manifold of the engine and controlled by the pressure therein andselectively controlling the pressure differential between said chambers.

5. A diverter valve system for use in association with a pump system fora vehicle having an internal combustion engine with an intake manifoldfor selectively diverting the air outflow of a positive output pressureair pump from a utilization system to a diversion system comprisingfirst and second chambers divided by a movable wall which moves underthe control of the air-pressure-differential between said chambers, adiverter valve controlled by said movable wall, and separate valve meanshaving a third chamber connected to the intake manifold of the vehicleand a separate movable wall controlled by the pressure in the intakemanifold for selectively controlling the pressure differential betweensaid first and second chambers.

. 6. The combination of claim 5, in which said separate valve means isresponsive to the continuing existence of an absolute intake manifoldpressure differing from a preselected range of intake manifold pressuresfor changing the pressure differential between said chambers in a senseto produce an opening force upon said diverter valve.

7. The combination of claim 6, in which said separate valve meansfunctions in response to the continuing existence of an absolutepressure in the intake manifold which is less than said preselectedrange of values.

8. The combination of claim 7, in which said separate valve meansmodulates the air pressure differential between said chambers inaccordance with the magnitude of the absolute pressures of the intakemanifold to which it is responsive to modulate the action of saiddiverter valve.

9. The combination of claim 6, in which said separate valve meansfunctions in response to the continuing existence of an absolutepressure in the intake manifold which is greater than said preselectedrange of values.

10. The combination of claim 9, in which said separate valve meansmodulates the air pressure differential between said chambers inaccordance with the magnitude of the absolute pressures of the intakemanifold to which it is responsive to modulate the action of saiddiverter valve.

11. The combination of claim 6, in which said separate valve means isresponsive to selected abrupt decreases of the absolute pressure in theintake manifold and establishes an air pressure differential betweensaid chambers in a sense to abruptly open said diverter valve.

12. The combination of claim 11, in which said separate valve meansopens in response to said selected abrupt decreases of the absolutepressure, in which means are provided for rapidly closing said separatevalve means thereafter, and in which means are provided effectivethereafter for reducing said air pressure differential to zero over aperiod of time.

13. The combination of claim 1 further including valve means, and inwhich said movement of said first mentioned movable wall in said onesense actuates said valve means to disconnect said first chamber fromsaid pressure from the pump and to disconnect said second chamber fromsaid pressure from said pump.

14. The combination of claim 13, in which said disconnection establishesa pressure in said first chamber which is affected by the back pressureof the utilization device.

15. The combination of claim 13, in which said movement of said firstmentioned movable wall in the opposite sense reconnects said firstchamber to said pressure from the pump and reconnects said secondchamber to said pressure from the pump through said orifice.

16. In a system including a vehicular engine and an emission controlsystem therefor in which the operation of the emission control systemshould be modified in response to selected changes in engine conditions,said vehicular engine including an intake manifold having a variablepressure, said emission control system including an air pump having avariable pressure, means for deriving an indication which varies atleast at times as a function of the variable pressure of the intakemanifold, means for deriving an indication which varies at least attimes as a function of the variable pressure of that pump, and valvemeans controlled by the relation between said indications forcontrolling the emission control system, said vehicular engine furtherincluding an exhaust manifold having'a variable pressure, furtherincluding means for deriving an indication which varies at least attimes as a function of the variable pressure of said exhaust manifold,said valve means being further controlled by the relation between saidlast mentioned indication and the indication which varies as a functionof the variable pressure of the intake manifold.

17. In a system including a vehicular engine and an emission controlsystem therefor including an air pump in which the operation of theemission control system should be modified in response to selectedchanges of engine conditions, and in which said engine conditions alsochange with changes of the altitutde of the vehicle, said first sensingmeans for sensing the selected changes of engine conditions, valve meanscontrolled by said first sensing means for controlling the operation ofthe emission control system, and means including second sensingmeans forsensing the changes of the altitude of the vehicle and for modifying theoperation of said valve means in a sense to at least partiallycompensate said valve for the changes of said engine conditions due tochanges of the altitude of said vehicle, said valve means selectivelydisabling said air pump for a period of time, said means including saidsensing means varying the length of said time in accordance with changesof the altitude of the vehicle.

18. The combination of claim 17 in which the output pressure of the airpump varies with changes of the altitude of the vehicle, and in whichsaid sensing of the changes of the altitude of the vehicle isaccomplished by sensing at least at times the output pressure of the airpump.

19. The combination of claim 17 in which the emission control systemincludes a conduit connected to the exhaust manifold of the vehicularengine and in which said sensing of the changes of the altitude of thevehicle is accomplished by sensing at least at times the pressure insaid conduit.

20. The combination of claim 17 in which the output pressure of the airpump varies with changes of the altitude of the vehicle and furtherincludes a conduit connected to the exhaust manifold of the vehicularengine, and in which said sensing of the changes of the altitude of thevehicle is accomplished at times by sensing the output pressure of theair pump and at times by sensing the pressure in said conduit.

1. A diverter valve system for selectively diverting the air outflow ofa positive output pressure air pump from a utilization system to adiversion system comprising first and second chambers divided by amovable wall which moves under the control of the air pressuredifferential between said chambers, a diverter valve controlled by saidmovable wall, means connecting said first chamber to said pressure fromthe pump, means including an orifice for connecting said second chamberto said pressure from the pump, and means for selectively momentarilyreducing the air pressure in said second chamber, said momentaryreduction of the air pressure in said second chamber producing movementof said movable wall in one sense, said movable wall moving in theopposite sense following said momentary reduction of the air pressure insaid second chamber under the control of said means including an orificefor connecting said second chamber to said pressure from the pump. 2.The combination of claim 1, in which said diverter valve, in operation,diverts the air from the pump to atmosphere.
 3. The combination of claim1, in which said diverter valve diverts the air from the pump to theinput to the pump.
 4. The combination of claim 1, in which said divertervalve system is associated with an automotive engine having an intakemanifold and in which said means for selectively momentarily reducingthe air pressure in said second chamber comprises separate valve meansconnected to the intake manifold of the engine and controlled by thepressure therein and selectively controlling the pressure differentialbetween said chambers.
 5. A diverter valve system for use in associationwith a pump system for a vehicle having an internal combustIon enginewith an intake manifold for selectively diverting the air outflow of apositive output pressure air pump from a utilization system to adiversion system comprising first and second chambers divided by amovable wall which moves under the control of theair-pressure-differential between said chambers, a diverter valvecontrolled by said movable wall, and separate valve means having a thirdchamber connected to the intake manifold of the vehicle and a separatemovable wall controlled by the pressure in the intake manifold forselectively controlling the pressure differential between said first andsecond chambers.
 6. The combination of claim 5, in which said separatevalve means is responsive to the continuing existence of an absoluteintake manifold pressure differing from a preselected range of intakemanifold pressures for changing the pressure differential between saidchambers in a sense to produce an opening force upon said divertervalve.
 7. The combination of claim 6, in which said separate valve meansfunctions in response to the continuing existence of an absolutepressure in the intake manifold which is less than said preselectedrange of values.
 8. The combination of claim 7, in which said separatevalve means modulates the air pressure differential between saidchambers in accordance with the magnitude of the absolute pressures ofthe intake manifold to which it is responsive to modulate the action ofsaid diverter valve.
 9. The combination of claim 6, in which saidseparate valve means functions in response to the continuing existenceof an absolute pressure in the intake manifold which is greater thansaid preselected range of values.
 10. The combination of claim 9, inwhich said separate valve means modulates the air pressure differentialbetween said chambers in accordance with the magnitude of the absolutepressures of the intake manifold to which it is responsive to modulatethe action of said diverter valve.
 11. The combination of claim 6, inwhich said separate valve means is responsive to selected abruptdecreases of the absolute pressure in the intake manifold andestablishes an air pressure differential between said chambers in asense to abruptly open said diverter valve.
 12. The combination of claim11, in which said separate valve means opens in response to saidselected abrupt decreases of the absolute pressure, in which means areprovided for rapidly closing said separate valve means thereafter, andin which means are provided effective thereafter for reducing said airpressure differential to zero over a period of time.
 13. The combinationof claim 1 further including valve means, and in which said movement ofsaid first mentioned movable wall in said one sense actuates said valvemeans to disconnect said first chamber from said pressure from the pumpand to disconnect said second chamber from said pressure from said pump.14. The combination of claim 13, in which said disconnection establishesa pressure in said first chamber which is affected by the back pressureof the utilization device.
 15. The combination of claim 13, in whichsaid movement of said first mentioned movable wall in the opposite sensereconnects said first chamber to said pressure from the pump andreconnects said second chamber to said pressure from the pump throughsaid orifice.
 16. In a system including a vehicular engine and anemission control system therefor in which the operation of the emissioncontrol system should be modified in response to selected changes inengine conditions, said vehicular engine including an intake manifoldhaving a variable pressure, said emission control system including anair pump having a variable pressure, means for deriving an indicationwhich varies at least at times as a function of the variable pressure ofthe intake manifold, means for deriving an indication which varies atleast at times as a function of the variable pressure of that pump, andvalve means controlled by the relaTion between said indications forcontrolling the emission control system, said vehicular engine furtherincluding an exhaust manifold having a variable pressure, furtherincluding means for deriving an indication which varies at least attimes as a function of the variable pressure of said exhaust manifold,said valve means being further controlled by the relation between saidlast mentioned indication and the indication which varies as a functionof the variable pressure of the intake manifold.
 17. In a systemincluding a vehicular engine and an emission control system thereforincluding an air pump in which the operation of the emission controlsystem should be modified in response to selected changes of engineconditions, and in which said engine conditions also change with changesof the altitutde of the vehicle, said first sensing means for sensingthe selected changes of engine conditions, valve means controlled bysaid first sensing means for controlling the operation of the emissioncontrol system, and means including second sensing means for sensing thechanges of the altitude of the vehicle and for modifying the operationof said valve means in a sense to at least partially compensate saidvalve for the changes of said engine conditions due to changes of thealtitude of said vehicle, said valve means selectively disabling saidair pump for a period of time, said means including said sensing meansvarying the length of said time in accordance with changes of thealtitude of the vehicle.
 18. The combination of claim 17 in which theoutput pressure of the air pump varies with changes of the altitude ofthe vehicle, and in which said sensing of the changes of the altitude ofthe vehicle is accomplished by sensing at least at times the outputpressure of the air pump.
 19. The combination of claim 17 in which theemission control system includes a conduit connected to the exhaustmanifold of the vehicular engine and in which said sensing of thechanges of the altitude of the vehicle is accomplished by sensing atleast at times the pressure in said conduit.
 20. The combination ofclaim 17 in which the output pressure of the air pump varies withchanges of the altitude of the vehicle and further includes a conduitconnected to the exhaust manifold of the vehicular engine, and in whichsaid sensing of the changes of the altitude of the vehicle isaccomplished at times by sensing the output pressure of the air pump andat times by sensing the pressure in said conduit.